Prior art systems have addressed the issue of DC-DC converter tuning by manually adjusting the controller response through a means convenient and accessible to the user e.g. see reference [1], listed below. In below listed reference [2] it was recognized that a DC-DC conversion power stage had properties that led to a convenient method to scale a pre-designed compensator so that its open-loop crossover frequency and phase margin remained approximately constant as power stage parameters varied, lending itself to manual tuning by the end user without having to re-design the compensator.
Adaptive control methods have been applied to the problem of DC-DC converter tuning. In below listed references [3] and [4], non-parametric methods were applied, involving the addition of a sinewave disturbance (reference [3]) or induced loop oscillation (reference [4]) into the system to measure the loop characteristics such as phase margin. However, these methods may be affected by outside disturbances which may be common in Point of Load regulation applications for example, and furthermore, may introduce noticeable disturbances on the output voltage affecting regulation performance.
In below listed reference [5], a model reference impulse response method is introduced in which two methods are proposed to characterize the impulse response of the system involving a one-time fast characterization of the system and a long-term statistical characterization. Whilst the statistical method proposed in below listed references [5] and [6] can be used online, the convergence time is too long for many applications due to the length of the required noise sequence and the introduced noise disturbance may be undesirable. The impulsive perturbation method suggested in reference [5] requires an experimental impulse to be introduced repeatedly whilst a 2-parameter search is carried out to determine the regulator parameters. This introduces disturbances during the tuning, suffers from similar drawbacks to references [3, 4] regarding sensitivity to outside disturbances and non-optimum convergence in the presence of noise.
The controller of below listed reference [7] shows how an LMS filter can be used in a feedforward controller to tune a single gain but does not address the issue of adaptive control of the general transfer function of the regulator. That issue is addressed in below lisated references [8] and [9] where a prediction error filter (PEF) is used to tune the loop based on minimisation of the power of the prediction error. However, the pseudo-open loop requirement for controller adaptation may lead to initial output voltage regulation being far less than required, and the two-parameter control system may be prone to divergence and therefore an unstable controller may result in certain circumstances. These issues are addressed in below listed reference [10] where the PEF is utilised to adjust the balance between two controllers. But there are several drawbacks, for example: i) the requirement to pre-design and to implement two controllers is over complicated for many users;
ii) the iterative minimisation of the prediction error takes some time which means that regulation is compromised during the convergence time because the controller is initially too conservative;
iii) the requirement for common state variables in the two fixed controllers means they cannot be integral controllers and this lack of a capability to vary the integral gain of the controller is a limiting factor in preserving the pulse response of the system.
Also references [8], [9] and [10] are all limiting the type of control structure to ARMA (zero/pole/non-integral) type structures with a feedforward element for steady-state regulation. The vast majority of controllers are PID and there is a distinct advantage in being able to tune or adjust PID compensators automatically without limitation.
PCT/EP2014/063987 relates to a method to adjust a compensator across the end users design space, e.g. output capacitance, and a means for the end user to configure the compensator such that the most suitable adjustment value is selected. Considering that it is advantageous to retain the response of the original system whilst a power stage parameter is changed, e.g. the capacitance C, it is desired to determine the manner in which the compensator must change in order to achieve a similar response. That is, this objective may be realized by designing a base compensator in the usual way, and devising a means to alter the compensation according the new value of C for example so as to maintain system performance. It has been shown that this relationship can be maintained, for example, if the proportional gain Kp, the integral gain Ki and and the differential gain Kd of a PID controller are altered from the original values in the following manner:F=Cnew/C, Kinew=Ki*sqrt(F),Kdnew=Kd*F, Kpnew=Kp*F, where Ki, Kp and Kd represent the gains of the original PID controller (i.e. original set of compensator coefficients), Kinew, Kpnew, Kdnew represent the altered values respectively to maintain the system response and Cnew and C represent the new and original value of the bulk capacitance. It will be clear that the capacitance C is being used as an example and the system is not limited in this regard but can also adjust for variations in other parameters (e.g. L), in a similar way.